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The $\phi^4$ theory on a hypercubic lattice with $d$ space-time dimensions is "trivial" for $d\geq 4$, in the sense that it reduces to a free non-interacting theory in the limit that the lattice spacing goes to zero. A rigorous proof for $d=4$ has been published only recently (2021), by Aizenman and Duminil-Copin in Marginal triviality of the scaling limits of critical 4D Ising and $\phi^4$ models. A proof for $d>4$ was obtained earlier (1981), by Aizenman.